Landsat 8 is an American Earth observation satellite launched on February 11, 2013. It is the eighth satellite in the Landsat program; the seventh to reach orbit successfully. Originally called the Landsat Data Continuity Mission (LDCM), it is a collaboration between NASA and the United States Geological Survey (USGS). NASA Goddard Space Flight Center in Greenbelt, Maryland, provided development, mission systems engineering, and acquisition of the launch vehicle while the USGS provided for development of the ground systems and will conduct on-going mission operations.https://en.wikipedia.org/wiki/Landsat_8

Look at the guide Study of Planets Solar System-1. These are all the new models of satellites for Earth exploration developed by Toutatis and Gironde.I have a question: "Why is the name of one satellite written with a hyphen, and the other without a hyphen?"

This is Toutatis who is in the right. Norad Satcat and n2yo.com write Landsat 7 and Landsat 8. On the wiki they write Landsat-7 and Landsat-8.

This is not very important, just agree on the type of writing for everyone.

It is enough to edit the ssc concerned, that of the possible objects revolving around and for those using LUT5 it is necessary to edit the guide and to modify the target of the button.

When you download an add-on, there is always to check the adaptation to your own Celestia system (avoid conflicts with other add-on). It should not be forgotten that some satellites have the same name as planets, moons, asteroids or places on planets.

There are many satellites of which we do not have a 3D representation.Among them there is Telstar 1, Hipparcos and Gaia. So I thought we could still capture their orbital parameters to see their orbits and names appear on Celestia's screen. So I made a generic 3D file represented by an "X". This cmod file has the advantage that it can be used for all non-existent 3D files. After that you just have to edit the ssc files with the help of the Norad or Horizon Satcat from Nasa's JPL (or n2yo.com).

Added after 9 minutes 54 seconds:Let's build the youngest telescope with the simplest geometric shapes? This is Gaia's telescope!

Model of Gaia Paris Air Show 2013. User:Pline

On April 25, 2018, the European Space Agency published on its website [23] the most detailed three-dimensional map of our galaxy in the history of mankind, containing information on the exact location and movement of almost 1.7 billion stars, as well as about 14 thousand asteroids of the solar system. The second data set (English Data Release 2, DR2) was held from July 25, 2014 to May 23, 2016. It is planned that Gaia will transmit information to Earth until 2020 to improve the 3D map

I have TGO spacecraft in Celestia from the start of this year... I sent this model to Croc even... here is other add-on of it... 3d model by Wieczor... SSC- file by myself... orbital elements from HORIZONS (NASA)

just finished work with WFIRST (Wide Field Infrared Survey Telescope) model by NASA... this is ready for Celestia now... but it will start in 2020...

The Wide Field Infrared Survey Telescope (WFIRST) is a NASA infrared space observatory that was recommended in 2010 by United States National Research Council Decadal Survey committee as the top priority for the next decade of astronomy. On February 17, 2016, WFIRST was formally designated as a mission by NASA.https://en.wikipedia.org/wiki/Wide_Field_Infrared_Survey_Telescope